1. Field of the Invention
This invention relates to a sensor assembly for measuring a weight force applied to a vehicle seat. Specifically, a sensor arrangement is integrated into a bracket that is mounted between a seat structure and a vehicle structure.
2. Related Art
Most vehicles include airbags and seatbelt restraint systems that work together to protect the driver and passengers from experiencing serious injuries due to high-speed collisions. It is important to control the deployment force of the airbags based on the size of the driver or the passenger. When an adult is seated on the vehicle seat, the airbag should be deployed in a normal manner. If there is an infant seat or a small adult/child secured to the vehicle seat then the airbag should not be deployed or should be deployed at a significantly lower deployment force. One way to control the airbag deployment is to monitor the weight of the seat occupant.
Current systems for measuring the weight of a seat occupant are complex and expensive. One type of system uses pressure sensitive foil mats mounted within the seat bottom foam. Another system uses sensors placed at a plurality of locations within the seat bottom. The combined output from the mats or the sensors is used to determine the weight of the seat occupant. If the sensors become damaged or fail to operate for some reason, the system will not provide accurate seat weight measurements and airbag deployment could occur under undesirable conditions.
Also, mounting these types of sensor systems within the seat can be difficult and time consuming. It is difficult to find mounting locations for each the sensors that will accommodate all of the various positions of a seated occupant while still providing accurate measurements. Further, shifting of the occupant on the seat can dislodge or move the sensors out of their proper location. Because the sensors are mounted within the seat bottom, it is difficult to reposition the sensors after the seat is installed in the vehicle.
In order to address issues such as these, another type of sensor system was developed, which did not require sensors to be place within the seat bottom. This other system individually mounted strain gages at each c of the seat. But, the installation of this type of sensor system can also be difficult and time consuming. Each strain gage sensor assembly is mounted to a separate mount. Then each mount must be individually installed at the seat corners.
Thus, it is desirable to have a simplified sensor assembly for measuring seat occupant weight, which decreases assembly time and cost. The system should further provide accurate measurements and be easy to service and maintain as well as overcoming the above referenced deficiencies with prior art systems.
A sensor assembly for measuring seat occupant weight is integrated into a mounting bracket that is installed on the inboard and outboard sides of a vehicle seat between a seat structure and a vehicle structure. Each mounting bracket includes at least one deflectable portion that supports a sensor assembly. A mount interface on the deflectable portion secures the bracket to the seat structure while mounting portions are located at opposing ends of the bracket to secure the bracket to the vehicle structure. The seat structure can be a seat track or seat pan and the vehicle structure can be vehicle floor or riser assembly that vertically positions the seat to a desired height.
In a disclosed embodiment of this invention, each bracket includes a pair of deflectable portions with one deflectable portion near the front of the seat and one deflectable portion near the rear of the seat. A central body portion extends between the pair of deflectable portions. The deflectable portions are movable relative to the central body portion due to input from the seat structure. The mounting portions, deflectable portions, and central body portion are all formed together as a unitary member.
Preferably the sensor assembly includes at least one strain gage mounted at each deflectable portion. Thus, in the preferred embodiment, a pair of strain gages would be located on the inboard side of the seat and a pair of strain gages would be located on the outboard side of the seat. The strain gage is mounted on the deflectable portion between the mount interface and the central body portion and measures the strain on the deflectable portion resulting from weight forces exerted on the seat.
Data from the sensor assembly is sent to an electronic control unit to identify and classify the seat occupant. The control unit can then control deployment of safety devices, such as an airbag, based on the weight forces as measured by the sensor assembly.
Integrating the sensors into the bracket simplifies assembly time as only one bracket with multiple sensors is installed on each side of the seat. These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.